The inventive concept relates generally to semiconductor memory devices. More particularly, the inventive concept relates to a nonvolatile memory device having a three-dimensional (3D) structure and related methods of operation.
Semiconductor memory devices can be roughly divided into two categories according to whether they retain stored data when disconnected from power. These categories include volatile memory devices, which lose stored data when disconnected from power, and nonvolatile memory devices, which retain stored data when disconnected from power. Examples of volatile memory devices include static random access memory (SRAM), dynamic random access RAM (DRAM), and synchronous DRAM (SDRAM). Examples of nonvolatile memory devices include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable and programmable ROM (EEPROM), flash memory device, phase-change RAM (PRAM), magnetic RAM (MRAM), resistive RAM (RRAM), and ferroelectric RAM (FRAM). Flash memory is a type of EEPROM and it is generally formed in one of two configurations to produce NOR-type flash memory or NAND-type flash memory.
In an effort to increase the storage capacity of flash memory devices, researchers have developed a three-dimensional (3D) array structure in which arrays of flash memory cells are stacked on top of each other. The development of reliable, high performance 3D array structures is an ongoing process and stands to benefit from continuing innovation.